A lubricating structure for a transmission disclosed in JP2000-81117A includes an axial hole formed penetrating through a gear shaft in an axial direction thereof to establish communication therethrough and plural oil holes provided on the gear shaft in a radial direction thereof to establish communication between the axial hole and an outside of the gear shaft. Through the plural oil holes, lubricant is supplied, for example, to a transmission gear fitted onto the gear shaft.
In FIG. 5, a direction of each arrow indicates a direction of a lubricant flow and a size of each arrow indicates an amount of the lubricant.
Referring to FIG. 5, the lubricant supplied from a right side (i.e., an upstream side) of the axial hole 12 is subject to a centrifugal force of rotation of the gear shaft 11 and flows out of the oil holes 13 due to the centrifugal force. Thus, a portion 10 needing lubrication, for example, a bearing, provided at a left side (i.e., a downstream side) of the axial hole 12, may not be sufficiently lubricated.
A need thus exists for a lubricating structure for a transmission, which is not susceptible to the drawback mentioned above.